Ultraviolet light can drive both useful and detrimental chemistry. Useful chemistry can include activating oxygen, e.g., forming ozone, which activated oxygen can subsequently be used for other purposes such as cleaning optics. It should be noted that although the activation of oxygen may be desirable, the activated oxygen may have some detrimental effects such as attacking adhesive polymers. Detrimental chemistry driven by UV light alone, i.e., without the oxygen, can include degrading polymers and turning contaminants into graphite.
Optical assemblies are used in a wide variety of industries. Through the course of fabrication, assembly and operation, the optical assemblies and optical elements included therein are exposed to a number of contaminants. The contaminants affect both the performance and the overall life span of the assembly and the discreet elements. While current cleaning techniques are largely effective, the UV light in the current method can cause deposits to form on the optical assembly and/or elements, e.g., graphite deposits, thereby causing permanent damage and shortened lifespans.
The current standard in cleaning optical assemblies involves ozone generation by passing UV light through the optical assembly while simultaneously passing an oxygen containing purge gas through the optical assembly. Thus, diatomic oxygen is exposed to ultraviolet radiation within the optical assembly. Typically, optical assemblies have an ultraviolet light source built into the unit and a purge gas stream containing oxygen gas flowing through the optical assemblies. Ozone is generated when the purge gas stream, containing oxygen, is introduced into the assembly and is exposed to UV light. The oxygen reacts with the UV light causing the formation of ozone and oxygen radicals in the optical assembly. These two components, ozone and oxygen radicals, are powerful oxidants resulting in an effective cleaning agent.
While the ozone and oxygen radicals clean the optical assembly, there are a number of side effects. For example, the adhesives in the optical assembly undergo accelerated degradation, i.e., UV light causes accelerated decomposition of adhesive polymers. This, in combination with the already high oxidation effect of the ozone and oxygen radicals, causes the adhesives to degrade at an accelerated rate, significantly decreasing the life span of the optical assembly. Moreover, the current technology can cause graphite deposits on an optical element, contributing to decreased lifespan of the optical assembly. The reaction between the contaminants and ultraviolet light causes the formation of graphite. The graphite gets deposited on the optic element, e.g., a lens. However, there is currently no way of easily removing the graphite from the lens without potential further damage to the lens; therefore, the deposit can be effectively permanent. Graphite deposits absorb UV light during operation and can cause permanent coating damage, i.e., the performance of the lens is decreased. Furthermore, the propagation of the ultraviolet light into the optical assembly makes this method of ozone generation ineffective in cleaning the assembly walls. The ultraviolet light generally enters at the top of the optical assembly, e.g., above the lens. The purge stream is directed around the optic. As the ozone is created, it cleans the wall of the assembly and the top of the lens in the general vicinity of the entry point for the purge stream.
Although ozone may remain stable for a reasonable length of time, i.e., it can travel some distance, oxygen radicals are very reactive and will react with the first surface contacted. At times, the ozone will convert to diatomic oxygen before it can reach the small crevasses between the adhesive or the underside of the lens. Therefore, because the ozone may break down before it can spread to the entire assembly, the known methods are ineffective in cleaning the entire optical assembly.
The generation of ozone is known in the art. In fact, ozone is the preferred method of cleaning in many industrial processes. However, ozone is not stable enough to enable bulk storage and transportation. Therefore, ozone must be produced near its location of use. Existing methods of generating ozone are generally effective and permit cleaning in an industrial setting; however, the known methods of ozone generation for optical assembly cleaning have several side effects that decrease the life span of the optical assembly. For example, known methods of ozone generation produce “dirty” ozone which includes contaminants that drive the contamination of optics that contact the “dirty” ozone. Furthermore, ozone is of great importance in an industrial setting as it is highly effective in removing contaminants, especially spores and microbes.
Thus, there is a long felt need for an optimized high purity ozone generating assembly constructed completely of industry standard materials used for the cleaning and recovery of optical assemblies which ozone generating assembly produces ozone that does not leave behind harmful contaminants.